DC-DC converters are common electronic components that take a first input voltage and convert it into one or more output voltages. This allows a user to take, for example, a higher battery voltage, such as 48 volts, and convert it down to a first and second output voltage, such as 12 volts and 5 volts, enabling the higher voltage DC source to be used to power various circuits that require lower voltage. Such a converter can provide either a single output voltage or multiple voltage outputs. One of the primary operating concerns of DC-DC power converts is the generation of heat, which can compromise the performance of and potentially damage electronic components, particularly within the confined spaces of modern electronic systems.
The trend in power devices is to deliver more power within a smaller volume of space (power density). As this trend of increased power density continues, there is a greater demand for better thermal management, which is becoming a larger percentage of the total cost of the product.
Several methods and component configurations have been used in the past to facilitate the dissipation of heat from DC-DC converters. Typical thermal management methods involve transferring heat through the top surface of the power converter and rely on conduction and convection heat transfer. The most common methods involve some form of thermal interface material coupling the top surface of the power converter to a case or baseplate. A heatsink is often mounted onto the case/baseplate to enhance convection cooling to ambient air (see FIG. 2). Another common method in applications involving little to no forced airflow is to conduct the heat from the top surface of the power converter through a thermal interface material to a metal surface that is typically part of a clamshell assembly.
The prior art methods described above normally involve some machining or forming of metal to fit with the profile of the power converter and to create the heatsink/clamshell. Depending on the size, material and manufacturing method used, it can get considerably expensive to implement these methods. These methods of thermal management also add weight to the converter, which can result in additional stress to the converter structure. Special care also needs to be given to the assembly and sequence of assembly to minimize stress on the converter solder joints.
Because the prior art methods transfer heat from the top surface to the environment, the converter needs to be designed in a specific way to take full advantage of this approach. Therefore, heavy power dissipating parts and/or temperature sensitive parts need to be placed on the top side of the converter in order for the above thermal management methods to have maximum benefit. Unfortunately, this requirement considerably reduces the design flexibility of the layout of the power module.
With power converters measured by watts/dollar, there is increasing demand for lower cost thermal management with each new generation of products. With higher power densities and smaller form factors, thermal management solutions need to have as small a footprint as possible.